Rubber hydrochloride film



May 1l, 1948. H. J. os'rl-:RHOF 2,441,328

.RUBBER HYDROCHLORIDE FILM Filed May 2o, 1945 .www

Patented May 11, 1948 RUBBER HYDROCHLORIDE FILM Harold Judson osrhof. 'Cuyahoga raus, ohio, Corporation, Akron, Ohio, a corporation of Delaware Application May 20, 1943, Serial No. 487,723

assignor to Wingfoot relates to the reuse in the process of solvent recovered in the manufacture of llm.

Rubber hydrochloride nlm has been made by dissolving rubber in a low-boiling solvent, suchv as benzene or chloroform, etc.; gassing the 8 Claims. (Cl. 26o-H771) cement with hydrogen chloride gas to form rubber hydrochloride; and then after purification of I the resulting rubber hydrochloride cement by neutralizatiometc., casting the. cement as a fllm and evaporating the solvent. For most purposes, the solvent recovered can be reused for the solution of further quantities of rubber for the manufacture ofrubber cement so that the process is cyclic. However, it has been found that the iilm so produced contains a contaminating material, herein referred to as the contaminant, which has a deleterious eflect on the flavor of foodstuiis packaged in the film. For instance, processcheese filled into a bag of such film while the cheese is hot and fluid acquires an oi taste due to the contaminant. It similarly affects other foods packaged in the film, such as milk, nuts, etc.

It appears from a careful study of this situation that the contaminant is an ingredient or the reaction product of an ingredient which occurs naturally in rubber. Although it has a relatively high boiling point, its vapor pressure is such that it is largely evaporated from the cast film with the solvent and is collected as an impurity in the recovered solvent. The solvent may, for example, be recovered in an absorbent charcoal,

Asolvent recovery system or any type of condenser.

'If an absorbent charcoal, solvent recovery system' is used, the solvent will be recovered for reuse in the usual manner; viz., by steam distillation. The contaminant is probably composed of phenolic materials occurring naturally in the rubber and may comprise amine decomposition products resulting from hydrolysis of the protein. It is also possible that it'may contain sterols or other natural antioxidant present in the rubber.

According to the present invention, the contaminant is removed from the cycle by distilling the recovered solvent before reuse at its boiling point or at a temperature approaching its boiling point. The contaminant is collected in the distillation residue, which is discarded. The condensed distillate is free from the contaminant or suciently free from the contaminant to be reused.

The process is illustrated in the accompanying flow sheet. This shows the use of solvent to dissolve the rubber to produce rubber cement. This 2 rubber cement is gassed with hydrogen chloride to' produce the rubber hydrochloride cement. This cement is cast as lm in the iilm apparatus, and the contaminated solvent which is volatilized from the nlm is recovered. It is subsequently subjected to a distillation process to separate the contaminant as residue and recover purified solvent for reuse in the process.

In general, the solvent may be reused once or twice without distillation without affecting the desirability of the resultinglm for food packaging. The diiilculty is not due to the contamination of the film from impurity present in the original solvent employed: it is due to the failure of all the high-boiling contaminant to volatilize with'the solvent in the drying of the film when the amount of contaminant naturally present in the rubber is augmented by additional contaminant present in the solvent from its previous use. There is contaminant present in the rubber, and this, of course, is carried over into the rubber hydrochloride cement. If the solvent used is free from contaminant or relatively free from contaminant, suiiicient of the contaminant present in the rubber hydrochloride cement will be volatilized from the rubber hydrochloride in the iliming apparatus to yield a lm which may be used in the packaging of foodstuis without imparting an off flavor to them. If too high a concentration of the contaminant is built up in the rubber hydrochloride cement by the reuse of contaminant-containing solvent, it is .not all separated from the iilm in the iilming and drying apparatus, but suiiicient of the contaminant is left in the nlm to make it undesirable for food packaging. Even with the final stages of. the film drier maintained at about 200v F., sufficient of the contaminant remains in the iilni to contaminate foodstuffs packaged in it. if too high a percentage of the contaminant is present in the rubber hydrochloride cement. The nlm may be removed from the drier and heated in air for some six to eight or more hours to remove the contaminant, but ordinarily this is not practical. The preferred method of operation is to use solvent suiilciently low in contaminant to allow volatilization of the contaminant from the rubber hydrochloride along with the solvent in the filming apparatus.

This application is a continuation of my application Serial No. 360,547, filed Gctober 10, 1940. now abandoned. y

What I claim is:

1.,' In the cyclic process of producing rubber hydrochloride film for use in the packaging of A ioodstuiis by dissolving rubber in a solvent, gassing the cement thus produced to form a rubber hydrochloride cement (which contains a highboiling contaminant), producing nlm from a cement of the rubber hydrochloride so formed by evaporating said solvent therefrom, and recovering and reusing said solvent to complete the cycle, the improvement which consists of distilling the recovered solvent before reuse to remove atleast the greater portion of said contaminant therefrom.

2. The method of preventing the concentration oi' impurities above the taste level in rubber hydrochloride film by distilling the solvent evaporated from a cast solution of the rubber hydrochloride prior to the reuse of said solvent, which comprises casting a solution of the rubber hydrochloride and evaporating solvent therefrom to produce rubber hydrochloride film. distilling evaporated solvent to separate high boiling residue therefrom, and then reusing the solvent for the preparation of a further solution of rubber hydrochloride to be cast as nlm.

3. The process of preventing the concentration of impurities in a cyclic process of producing rubber hydrochloride iilm which comprises dissolving rubber in a solvent, hydrochlorinating the solution. casting illm therefrom, and evaporating solvent to produce a i'llm of rubber hydrochloride, recovering the solvent, distilling the recovered solvent to separate it from high boiling residue contained therein, and reusing the solvent for solution of further rubber for repetition of the process.

4. That improvement in the cyclic process of producing rubber hydrochloride by dissolving rubber which contains an ingredient naturally occurring therein which after hydrochlorination and neutralization becomes a taste-imparting impurity which when the rubber solution has been hydrochlorinated and neutralized and then cast as a film and subjected to evaporating conditions will evaporate to at least some extent with the solvent and be recovered as a taste-imparting impurity in the condensate, which impurity on cyclic reuse of the condensate as a solvent for further rubber will build up in the solvent to such a level that on evaporation of the solvent from the cast rubber hydrochloride film, sumcient impurity will remain in the film to cause it to contaminate materials packaged in the iilm, which improvement comprises separating said impurity from the solvent by distillation of the solvent therefrom before the impurity content of the solvent has reached the aforesaid level.

5. 'I'he improvement in the cyclic process of producing rubber hydrochloride film in which a solution in benzene is produced from rubber and an ingredient naturally occurring in rubber, which on hydrochlorination and neutralization yields a taste-imparting impurity, the solution then being hydrochlorinated and neutralized, with subsequent casting of the solution as a film with eventual heating of the illm to about 200 F. to evaporate the benzene from the lm with simultaneous removal of some of the tasteimparting impurity, with condensation of they from the benzene by distillation of the beaune therefrom before reuse of the solvent so as to keep the impurity content of the solvent low enough to maintain the level of the impurity in the nlm below that at which products packaged therein become contaminated thereby.

6. The cyclic process of producing rubber hydrochloride nlm which comprises dissolving in |benzene rubber and an ingredient naturally occurring in rubber which on hydrochlorination and neutralization-yields a taste-imparting impurity, thenV hydrochlorinating and neutralizing the resulting hydrochlorinated solution, casting the solution as a nlm, evaporating solvent from the film. and heating the film at about '200 l".

to drive fout the benzene therefrom and simultaneouslyremoving at least some of the tasteimparting impurity from the film, condensing the benzene and taste-imparting impurityand then before reuse of the benzene in the cyclic production of rubber hydrochloride film distiiiing the mixture of benzene a`nd impurity to separate the benzene from the impurity and then reusing the benzene in the cyclic process.

7. The cyclic method of producing rubber hydrochloride i'ilm with lessening of the content therein of a taste-imparting impurityvpnoduced from an ingredient naturally occurring in rubber, by hydrochlorinatin and then neutralization thereof, whi-ch comprises dissolving rubber containing said ingredient, hydrochlorinating, and then neutralizing the solution, casting a nlm from the resulting solution, evaporating solvent from the film, and heating the iilm to facilitate such evaporation and simultaneously volatilizing from the film the taste-imparting impurity. condensing the resulting vapors to recover the soivent and condensing therewith the impurity, and thereafter separating the impurity by distillation of the solvent therefrom and reusing the solvent for solution of further rubber.

8. The cyclic method of producing rubber hydrochloride iilm while maintaining below an objectionable level the content therein of a tasteimparting impurity produced by hydrochlorinating and then neutralizing an ingredient naturally occurring in rubber, which comprises dissolving in benzene the rubber and said ingredient, hydrochlorinating and then neutralizing the solution, casting a. film from the resulting solution, evaporating the benzene from the film while at a temperature of about 200 F. and simultaneously volatilizing at least some of the taste-imparting impurity from the film, condensing the resulting vapors to obtain benzene contaminated with the REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number K Name u Date 2,067,971 Leach et al. Jan. 19, 1937 2,078,526 Calvert Apr. 27, 1937 2,134,172 Calvert Oct. 25, 1938 2,161,454 Calvert 1.. June 6, 1939 

